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arXiv 2301.09369quant-phcond-mat.other
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使用低深度变分量子算法绘制相图

Sketching phase diagrams using low-depth variational quantum algorithms

Jan Lukas Bosse, Raul Santos, Ashley Montanaro

AI总结:

研究利用低深度VQE算法绘制量子系统相图,发现低保真度基态近似即可较准确预测相变位置,并提出基于VQE能量随电路深度改善速度的模型无关相变预测器。

摘要:

由于模拟远离热力学极限的小型量子系统所需的计算资源巨大,使用经典模拟绘制量子系统的相图可能极具挑战或难以实现。我们研究了使用量子计算机和变分量子本征求解器(VQE)来完成此任务。与使用VQE制备精确基态不同,绘制相图可能需要较少的量子资源和精度,因为基态的低保真度近似可能足以正确识别不同的相。我们使用低深度VQE电路的经典数值模拟,计算了四个经过充分研究的自旋和费米子模型的序参量,这些模型涵盖了1D和2D系统,以及精确可解和经典难解系统。我们发现,即使VQE产生的状态与真实基态的重叠很小,也能以合理的精度预测相变位置。此外,我们引入了一种与模型无关的相变预测器,它基于VQE能量随电路深度提升的改善速度,并发现在某些情况下它也能预测相变。

英文摘要:

Mapping out phase diagrams of quantum systems using classical simulations can be challenging or intractable due to the computational resources required to simulate even small quantum systems far away from the thermodynamic limit. We investigate using quantum computers and the Variational Quantum Eigensolver (VQE) for this task. In contrast to the task of preparing the exact ground state using VQE, sketching phase diagrams might require less quantum resources and accuracy, because low fidelity approximations to the ground state may be enough to correctly identify different phases. We used classical numerical simulations of low-depth VQE circuits to compute order parameters for four well-studied spin and fermion models which represent a mix of 1D and 2D, and exactly-solvable and classically hard systems. We find that it is possible to predict the location of phase transitions up to reasonable accuracy using states produced by VQE even when their overlap with the true ground state is small. Further, we introduce a model-agnostic predictor of phase transitions based on the speed with which the VQE energy improves with respect to the circuit depth, and find that in some cases this is also able to predict phase transitions.

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